The objective of the research proposed in this application is the synthesis and biologic evaluation of imaging agents for the detection and differential diagnosis of carcinoma of the pancreas. This disease is responsible for the death of nearly 7000 persons annually in this country. Although surgical resection techniques for this organ have been perfected, their success relies heavily on early diagnosis. Unfortunately, early diagnosis is rarely achieved because the current agent used for pancreas imaging, Se75-labeled selenomethionine, has several shortcomings, prominent among which is a low pancreas to liver concentration ratio. Since these organs overlay one another, the pancreatic image is often obscurred. If a sharper pancreatic image could be obtained much earlier, diagnosis would be possible. Recent work has indicated that ring containing amino acids concentrate much more in the pancreas versus the liver than does selenomethionine. Preliminary studies in this laboratory not only have confirmed these reports, but also have implicated selenium-75 containing aromatic amino acids as agents likely to be far superior to selenomethionine in this regard. It therefore is proposed that selenium containing analogs of each of the aromatic amino acids (tyrosine, phenylalanine, tryptophan, and histidine) be synthesized for complete evaluation of their potential as new imaging agents for carcinoma of the pancreas. The prepared substances will be evaluated in animals to determine their pharmacokinetics, biologic distribution, toxicity, and ultimate fate. The stability of these agents will be investigated with double labeled samples (C14 or H3 in addition to the gamma emitting radionuclide). Any radiopharmaceutical emerging from this work which exhibits potential for effective pancreatic imaging in man then will be considered for evaluation in a clinical trial.